Endless belt conveyors, having motor-driven continuous belts extending over rotatable rollers, are widely used for transporting materials over relatively short distances. The faster these conveyor systems are operated, the more efficient the systems are because a greater amount of materials may be transported in the same amount of time. However, increasing the speed at which these conventional conveyors operate causes several problems. As the conveyor belt moves at increasing speeds along the rollers and the slider bed, the friction load, or drag, between the belt and the slider bed increases exponentially. Therefore an exponentially increased amount of energy is required in order to overcome the drag. The force required to overcome the drag at these higher speeds may result in the tearing of the endless belt.
Further, increasing the belt speed of conventional conveyor systems results in an exponential increase in the noise level produced by the rubbing of the conveyor belt along the slider bed and the rollers as well as by the rotation of the rollers themselves. If the noise level is too high, it can damage the hearing of individuals working in the vicinity of these conveyor systems. Therefore, the Occupational Safety and Health Administration has proposed regulations limiting the permitted noise level per conveyor to seventy-five decibels. Many conventional belt conveyors must be operated at relatively slow speeds in order to meet this proposed standard. Operating at these slow speeds results in substantial loss of productivity in transporting materials by conventional belt conveyors.
In addition to these problems, the length of the conveyor belt in conventional conveyor systems is limited. The limitation on the length of the belt is due to the fact that the force needed to overcome drag between the belt and the slider bed and rollers increases as the length of the conveyor belt increases. This also creates the danger of tearing of the belts in these systems. When prior art conveyors are used, three or four conveyors may be required to transport materials over a one-thousand foot pathway.
Another problem in the field of conveyor systems is that the variety of materials which may be transported is limited by the configuration of the systems. These systems require rollers to permit the belts to move along the length of the system. The required size of the rollers may vary with the weight and size of the materials being transported along the conveyor. Therefore, in order to transport materials of different weights and sizes along the conveyor, changes in roller size may be necessary in a conveyor system. Changing rollers is a very difficult and time consuming process in prior art systems because considerable disassembly and reassembly is required in order to gain access to the rollers so that they may be removed and replaced. This results in considerable down-time for the conveyor system while the rollers are replaced.
Further, because they are moving parts, the rollers of conveyor systems are subject to wear during normal use. Wear of the rollers requires periodic replacement of the rollers. In conventional belt conveyor systems, roller replacement due to wear requires disassembly and reassembly of the conveyor system to gain access to the rollers in the same manner as that required to change the size of the rollers. Replacing worn rollers in conventional conveyor system thus results in considerable downtime for the conveyor system as previously described for changing the size of the rollers.